The Söhlde Formation (Cenomanian, Turonian) of NW Germany: Shallow Marine Pelagic Red Beds
Published:January 01, 2009
Frank Wiese, 2009. "The Söhlde Formation (Cenomanian, Turonian) of NW Germany: Shallow Marine Pelagic Red Beds", Cretaceous Oceanic Red Beds: Stratigraphy, Composition, Origins, and Paleoceanographic and Paleoclimatic Significance, Xiumian Hu, Chengshan Wang, Robert W. Scott, Michael Wagreich, Luba Jansa
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The Söhlde Formation (Upper Cenomanian-lower Upper Turonian) of Lower Saxony and Sachsen-Anhalt is characterized by an alternation of red and white limestones of a pelagic biosedimentary system, deposited ca. 200 km distant from the nearest coastline on the European Cretaceous shelf sea at a paleolatitude around 45° N. Seven sedimentary cycles of ca. 430 ky duration can be recognized, each of which is separated by discontinuities and/or significant facies changes. White limestones and marl–limestone alternations were deposited mainly in intrashelf depressions and/or during relative sea–level highs. The red limestones were deposited on intrashelf swells above and shortly below storm wave base. Storm-and current-induced advective pore-water flow associated with low accumulation rates in a nutrient-depleted intrashelf swell setting (low Corg flux into the sediment) resulted in an excess of oxygen in the sediment column and an early diagenetic window, in which ferric iron minerals were generated, causing the red pigmentation. The source of the iron was most likely clay minerals, inasmuch as a positive correlation between clay content and red pigmentation is observed. No trace of microbial activity associated with the genesis of the red color can be confirmed yet.
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Cretaceous Oceanic Red Beds: Stratigraphy, Composition, Origins, and Paleoceanographic and Paleoclimatic Significance
The occurrence of marine red beds has been known for at least 140 years, since Stúr (1860) and Gümbel (1861) first described them from the Púchov beds in the Carpathians and the Nierental beds in the Eastern Alps. A few biostratigraphic and sedimentological studies followed, particularly in European countries. However, detailed investigations on paleoceanographic and paleoclimatic implications related to Cretaceous marine red beds were initiated by Prof. Chengshan Wang, Dr. Xiumian Hu, and their colleagues. This collection of papers resulted from two collaborative research projects funded in part by UNESCO/IUGS International Geosciences Project IGCP 463 and IGCP 494. The IGCP 463 “Upper Cretaceous Oceanic Red Beds: Response to Ocean/Climate Global Change” (2002-2006) was led by Prof. Chengshan Wang (China University of Geosciences, Beijing, China), Prof. Massimo Sarti (Universitá Politecnica delle Marche, Italy), Dr. Robert Scott (University of Tulsa and Precision Stratigraphy Associates, USA), and Prof. Luba Jansa (Dalhousie University, Canada). The objective of IGCP 463 was to study major paleoceanographic phenomena recorded by sedimentary sequences in the world oceans. Cretaceous deposition changed several times from widespread organic-carbon-enriched shales that indicate a dysoxic to anoxic deep ocean environment, to mostly reddish clays and marls deposited in an oxic marine environment during the Late Cretaceous.